Perspective drafting attachment



Nov. 23, 1948. F. L. GOFF 4,38

PERSPECTIVE DRAFTING ATTACHMENT Filed Jan. 17, 1947 Patented Nov. 23, 1948 UNITED STATES PATENT OFFICE PERSPECTIVE DRAFTING ATTACHMENT Francis Lee Goff, Bloomington, Ill., assignor of one-third to EdmundiE. Hurst and one-third to John WarrenPaxton, both of Bloomington, Ill.

Application January 17, 1947, Serial No. 722,495

- 2 Claims. 1

This invention relates to an attachment for standard drafting equipment for use in drawing perspective views.

The main objects "of this invention are, to provide an improved form of a simply constructed and easily usable attachment for the drawing of perspective views; to provide an improved attachment of this kind especially suitable for use with any of the standard drafting machines; to provide an improved construction and relative arrangement of straight-edges on an attachment of this kind for respectively determining the vertical and oppositely converging diagonal lines of a perspective view; to provide improved clamping means for temporarily holding the diagonally divergent straight-edges in any position; and to provide a perspective drawing attachment of this kind which is inexpensive to manufacture, which is easily assembled on a standard drafting machine, and which is positive in its operation.

A preferred form of perspective drafting attachment embodying this invention is shown in the accompanying drawings wherein:

Fig. 1 is a plan view of a drafting surface on the support for which is mounted a conventional type drafting machine wherewithisassociated this improved perspective drafting attachment;

Fig; 2-is a fragmentary perspective of the drafting machine head with this improved perspective drafting attachment arranged thereon;

Fig. 3 is an enlarged fragmentary plan view of the supporting plate for the improved perspective drafting attachment;

Fig. 4 is a further enlarged cross-sectional detail taken on the line 4-4 of Fig. 3;

Fig. 5 is a similar view taken on the line 5-5 of Fig. 3; and

Fig. 6 is an enlarged cross-sectional detail taken on the line 6-6 of Fig. 1.

The more modern and conventional type drafting machine I wherewith a perspective drafting attachment 8 constructed in accordance with this invention is particularly adapted for use comprises a straight-edge supporting-head 9 mounted for movement in a plane parallel to the drafting surface IIJ by means of a clamp support II and a pair of arms I2 and I3 pivotally connected together at I4. The clamp support II is secured to one edge-usually the upper edge-oi the drafting-surface support (not herein illustrated). The arm I2 pivotally supports the head 9 with which is associated a hand grip I5 and an annular scale I6. The arm I3 is pivoted at l1 to the supporting clamp II. straight-edge supporting-head in a predetermined Cables I8 and I9 serve to keep the angular'position withregard to vertical and horizon-tal dimensions of the drafting surface ID, as may be determined by a locking means (not shown) arranged between the hand grip I5 and scale IE on the one hand and the straight-edge supporting-head 9-on the other hand, which locking means is controlledby a release pin 20.

The head 9 is provided with a pair of rightangularly disposed chucks 2I and 22 each of which is adapted to removably support conventional straight-edges oneofwhich is shown at 23. When it is desired to use the machine for perspective drawing the straight-edge normally supported in the-chuck 22 is replaced by a perspective drafting attachment I embodying this invention. The improved perspective drafting attachment I comprises a member 25 on which is supported a chuck-receiving shank 26' and straight-edges 21, 28, and 29- and a locking'means 30.

The shank 26 is a wedge-like element with tapered sides adapted to fit in the chuck 22 and, being separately formed, is attached to the plate 25 by means of screws, as clearly shownin Fig. 3. The shank 26 thus supports the member 25 on the drafting machine head 9 so that the straight-edge 21 is at right angles to the straight-edge 23.

The straight-edge 21 is rigidly fixed on the plate 25' whereas the straight-edges 28 and 29 are pivoted to the member 25 on opposite sides of the straight-edge 21 These pivots are preferably in the form of pins 3| and 32- which, in Fig. 5, are shown to be setin recesses in the member 25 and do not extend" through said member. Spacing discs 33 are arranged concentricallyof the pins 3| and 32 on opposite sides of the straight-edges 28 and 29.

At their outer ends the straight-edges 28 and 29 are connected to the end. ofaflexible element 34 in the form of a coiled spring wire. This forms a loop which extends around rollers 35 and 36 mounted on the c-clamps 31 and 38. These clamps are adapted to .be secured to the edges of the support for the drafting surface I0 to simulate the vanishing points of a perspective. Thus they cause thespring 34 to locate the straight-edges 28 and 29 in proper angular position with respect head 9, the outer end of the lever 42 is contiguous to the release pin 20. This permits the lever 42 to be depressed by the thumb or a finger of the hand which usually is used for actuating the said release pin 29.

The operation of the attachment is thought to be more or less obvious from the foregoing'description and therefore to require only a general explanation.

When it is desired to use the drafting machine 1 forperspeotive drawings the usual straight-edge for drawing vertical lines on the drafting surface [0 is removed from the head 9 and this attachment 8 secured in its place. The C-clamps 31 and 38 will be relatively positioned on the support for the drafting surface It! as determined by the character, size, and position of the perspective to be drawn on the drafting surface It]. Normally the drafting head 9 would be set so that the straight-edge 21 occupies a position to draw vertical lines on the drafting surface I0. Once the station point for a particular perspective view has been determined the drafting machine I is actuated so as to move the straight-edges 21, 28,

and 29 into the positions desired to draw the lines 1 representing the vertical height and the length and the width of the object the perspective view of which is to be placed on the drafting surface.

The drafting machine having been set to draw the diagonal lines representing the length and width of the object, the lever or arm 42 is depressed. This shifts the bar 39 against the action of the spring 43 into contact with the upper spacing discs 33 on the straight-edges 28 and 29. The straight-edges 28 and 29 thereby are secured against accidental displacement during the drawing of lines along either of these straight-edges.

If perchance it is desired to set the straightedges 28 and 29 for the purpose of drawing of isometric representations, the knurled nut 41 may be turned down to shift the locking bar 39 into contact with the spacing disc 33 on the straightedges 28 and 29. This will hold the straightedges 28 and 29 against relative movement so long as the knurled nut remains in such position.

Variations and modifications in the details of structure and arrangement of the parts may be resorted to within the spirit and coverage of the appended claims.

I claim:

1. Drafting equipment comprising, a member formed with a shank adapted to fit a chuck, on a standard drafting machine a pair of straightedges pivotally attached to said member, and positionable in various divergent angular relationships to represent the lines for a perspective drawing a bar superimposed on said member on a pin positioned between said straight-edge pivots with the ends of said bar disposed over the pivoted ends of said straight-edges, resilient means normally urging said bar out of contact with said straight-edge ends, a lever arm associated with said pivot pin and actuatable for depressing said bar against the action of said resilient means to contact said bar with said straight-edge pivoted ends for temporarily locking said straight-edges against accidental displacement during the drawing of lines therealong.

2. Drafting equipment comprising, a member formed with a shank adapted to fit a chuck, on a standard drafting machine a pair of straightedges pivotally attached to said member, and positionable in various divergent angular relationships to representthe lines for a perspective drawing, a bar superimposed on said member on a pin positioned between said straight-edge pivots with the ends of said bar disposed over the pivoted ends of said straight-edges, resilient means normally urging said bar out of contact with said straighted'ge ends, a nut threaded on the upper end of said pivot pin, a lever arm having the inner end thereof interposed between said nut and said bar and having the outer end extending above at an incline to said member and actuatable for depressing said bar against the action of said resilient means to contact said bar with said straight-edge pivoted ends for temporarily locking said straight edges against accidental displacement during the drawing of lines therealong.

' FRANCIS LEE GOFF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 687,432 Lee Nov. 26, 1901 2,042,885 Fay June 2, 1936 2,358,521 Langsner Sept. 19, 1944 2,380,073 Robinson July 10, 1945 FOREIGN PATENTS Number Country 9 Date 311,098 Italy Sept. 21, 1933 

